Rasch analysis and ordinal-to-interval conversion tables for the Depression, Anxiety and Stress Scale.

Abstract

This study conducted Rasch analysis of the Depression, Anxiety and Stress Scale using responses of 400 participants to produce ordinal-to-interval conversion algorithms not available to date. Minor modifications such as removing the non-fitting item 5 and combining subscales items into super-items were necessary to achieve the best model fit ( χ2(15) = 20.28, p = 0.16). The results support internal validity of the modified 20-item Depression, Anxiety and Stress Scale and include ordinal-to-interval conversion tables for use with non-clinical populations that improve reliability and precision of the measure.